The properties of hydraulic fluid may be partially dependent on its temperature. For example, when the fluid is cold, it may have a high viscosity, whereas, when the fluid is relatively warmer, the fluid may have a lower viscosity. Work machines, such as skid steer loaders, often use hydraulic fluid to drive actuators and/or hydraulic motors to operate work implements and drive the loader from place to place. For example, a skid steer loader may flow hydraulic fluid through a valve to raise or lower a work implement. When the work machine is started after being idle, the fluid may be cold, and it may take up to an hour for the temperature to rise and stabilize at an operating temperature.
The temperature dependent properties of hydraulic fluid may affect the consistency and responsiveness of the work machine. For a given control signal, a flow-control valve opens a preset percentage, allowing a certain flow rate of fluid volume through the valve. Because the viscosity affects the flow properties of the fluid, for the same given control signal, the volume flow rate of fluid through the valve may be reduced when the fluid is highly viscous than when the fluid is relatively less viscous. Therefore, a command from an operator may cause a work implement to move at one speed when the hydraulic oil is cold and at a second different speed when the hydraulic oil is relatively warmer. Accordingly, the operator must adjust to the differences in responsiveness of the work machine due to the change in viscosity in the hydraulic fluid, which may cause inefficiencies.
U.S. Pat. No. 5,042,323 to Murano et al. discloses a hydraulic control method for a change gear mechanism for a vehicle. This control method includes operating a valve at a frequency to maintain a desired fluid pressure for a clutch system. The frequency of valve operation is incrementally changed as the temperature changes. However, the system disclosed in the '323 patent does not control a proportional flow to control a fluid-operated machine component. Accordingly, the system disclosed in the '323 patent may not provide consistency to a work machine dependent on flow control.
The method and system disclosed herein may provide a more consistent control of a work machine in a variable temperature environment.